Coffee (but Not Simply Caffeine) Mitigates Alzheimer's

One clue: they found that caffeinated coffee induces an increase in blood levels of a growth factor called GCSF (granulocyte colony stimulating factor) in mice. GCSF is greatly decreased in patients with Alzheimer’s disease and is demonstrated to improve memory in Alzheimer’s mice.

The researchers said this is not possible with other caffeine-containing drinks or decaffeinated coffee.

An increasing body of scientific literature indicates that moderate consumption of coffee also decreases the risk of Alzheimer’s, Parkinson’s disease, Type II diabetes, and stroke. Recent studies have reported that drinking coffee in moderation may also significantly reduce the risk of breast and prostate cancers.

The researchers suggest that moderate daily coffee intake (4 to 5 cups a day) starting at least by middle age (30s–50s) is optimal for providing protection against Alzheimer’s disease, although from their studies, starting even in older age appears protective.

Presumably various types of tea have been tested and found wanting in boosting GCSF. Low GCSF is definitely diagnostic for Alzheimers, and elevating GCSF improves symptoms some.

This is causal. Usually you just see correlations, which leave open the possibility that only if you’re the type of person who was already likely to drink coffee, would you benefit - if you drank coffee only because you heard it was correlated with better health, then it would not work for you.

There are definite short-term changes in thinking from coffee (and probably caffeine in general) that are more tradeoffs than unambiguous improvements (supposedly creativity and long-term learning are impaired) - LessWrong discussion.